A case report on myocarditis and right chamber dilation: cardiac magnetic resonance acquisition for accurate diagnosis.

We present the case of a 21-year-old male with chest pain, malaise, and fever, who was initially diagnosed with suspected acute myocarditis. The patient exhibited elevated cardiac troponin levels, occasional premature ventricular complexes, and right ventricular dilation, raising concerns about arrhythmogenic cardiomyopathy. Cardiac magnetic resonance (CMR) imaging showed myocardial edema and subepicardial enhancement in the basal anterolateral segment, confirming myocarditis, but also revealed severe dilation of the right chambers. Advanced imaging sequences identified a previously unrecognized inferior sinus venosus atrial septal defect (SVASD) with partial anomalous pulmonary venous return. This finding led to a significant left-to-right shunt and surgical correction was performed. SVASD, a rare congenital anomaly, often remains undiagnosed due to its subtle clinical presentation and limitations of standard imaging techniques. This case highlights the importance of tailored CMR acquisition protocols, which revealed a congenital heart defect in our patient despite an initial focus on myocarditis. The adjustment in diagnostic approach significantly altered the patient's management and may have improved his long-term prognosis.